Circuit breaking device



-July 7, 1936. E s, TRUE v 2,046,857

CIRCUIT BREAKING DEVICE Filed Jan. 13, 1953 *Im Edwin E. True Patented .lilly 7,1936

UNITED STATES PATENT 1 OFFICE crxilll'rrue, oakGPi-TIE Applicafinnigm'lS; N0. 651,539

This invention relates to electrical devices generally and is concerned particularly with electrical circuit breaking devices.

'I'he principal object of the invention is toprovide a simpler, more compact, and more reliable device of this character than has heretofore been available. This object .is attained by employing a novel control arrangement utilizing both electro-magnetic and electro-thermal action.

v A device of this character has many useful applications in the electrical art. For example, it may serve as a current limiting appliance performing thefunctions of an overload circuit breaker or fuse. It presents definite advantages over manually set circuit breakers and fuses in that it does not leave the circuit dead after the overloaded condition is corrected. The device may also serve as an interrupter for producing current pulsations of deinite frequencies. Other applications will be readily apparent to those skilled in the art.

One of the main features of the present invention is the arrangement whereby the opening and closing of a set of contacts is controlled both electro-magnetically and electro-'thermical- 1y. 'Ihis arrangement permits a positive opening vmovement and clean contact separation thereby minimizing the tendency to arc.

Another feature is the arrangement of the contacts themselves so as to minimize arcing. This arrangement contemplates the use 'of iiexible,

ically mentioned will be discussed in more detail 5 hereinafter in connection with the description of the device and its operatiomreference being had to the accompanying drawing comprising Figs. 1 to 4. Fig.,1 is a sectional view of one embodiment of the invention wherein a single set of contacts 50 is provided.x Fig. 2 is a sectional view of another embodiment of the invention wherein two sets voi' contacts are employed. Fig. 3 is an enlarged view showing the contact construction and supporting method employed. FigA is a circuit diagram of 55 a device constructed according to Fig. 1.

The construction of a preferred embodiment of the invention may be readily seen by reference to Figs. 1, 2, and 4 of the drawing. In these figures, the reference character I designates the usual insulating case provided for screw plug type 5 fuses. Outside contact connections to the holder terminal clips are provided by screw 3 and metallic shell 2. A metallic washer 23 serves to connect shell 2 with the thermo-iexible strip 4.

Multi-leaf contacts 5 and 'l are of the same genl0 eral type as the contacts disclosed in applicants prior Patent No. 1,769,279 `granted July 1, 1930. These contacts are rigidly fastened to thermoflexible strip l and bracket 8, respectively,'by rivets 22. An armature 6 of magnetic material 15 is also riveted to strip 4 and, if desired, may act as 4a. contact and 'current carrying leaf. Alternatively, the upper end of this strip may be provided with an insulator for preventing electrical contact with bracket 8 in which case the function' 20 'willbe that of an armature. In either arrangement the armature serves'V to focus the magnetic ux so as to distort and draw out any arc that may be established across the contacts. The distortion of an arc in a .magnetic eld is a well 25 known phenomenon, the theory of which need not be discussed in detail here. It is sufficient to note that, in the device comprising the present invention, the circuit opened by contacts 5 and 1 includes the inductive resistance of coil I0 so 30 that there is a relatively large magnetic ilux between the elements 6 and 8 immediately following contact separation. The contacts are within this magnetic field and any arc formed between them will be drawn out and extinguished by the magnetic flux. The bracket 8 is made of magnetic material, for example, soft iron or Allegheny metal, and serves bothas a current carrying element and as an element of the magnetic circuit of the coil. The bracket is in electrical contact with metallic washer 18, one side of which is bent up as shown to provide a suitable connection with conductor lll. The core 9 is preferably constructed of the same material as bracket 8. Conductor` lli may be of copper or other suitable conducting material, its size depending upon the current carrying capacity desired. The number of turns of conductor wound on core 9 are governed by the inductance desired and by the force to be -exerted on amature 6, which are in turn aV `function of the operating limit desired. The

lower end of conductor I0 is connected to a bent up portion of washer l'l which is in electrical contact with screw 3. Bracket I3 is made of the i same type of metal as core 9 andserves the double 55 purpose of providing an adjusting bearing for strip B and of reinforcing the magnetic path between core 9 and armature t. Screw 2i controls the adjustment Aof strip tl. by varying the tension` together by screws 3 and 2li which extend through insulating end pieces I9 and 2d to core Q.

The thermo-flexible strip d controls\the opening of contacts 5 1 by exing in such manner that contact 5- is moved out of engagement with contact 1 which is stationary. Armature 6 is also moved as strip 4 exes, this movement being opposed by the electro-magnetic force exerted by coil I0 prior tothe opening of the contacts. The thermo-ilexible strip is preferably composed of two laminae of diierent metals welded together along one surface. Bi-metallic material of a. suitable nature is well known in the art and is readily obtainable commercially.y A particularly suitable element is one in which the upper lamina consists of an iron alloy having magnetic properties. The lower lamina in this case will ordinarily consist of an alloyof copper although any Asuitable metal may be employed. The strip 'con'- stitutes one of the current carrying elements of the device as shown and is heated by the current flow therethrough. The extent of lexure and the torque exerted by the strip depend jointly on the dimensions thereof and the temperature attained. The temperatures to which predetermined currents will raise the strip are functions of its cross sectional area and eiective resistance., By prop- `er proportionment of these factors and by the application of the necessary mechanical tension on the contacts when no current is owingthe device can be made to open a circuit when any predetermined rate of current ow is exceeded. This arrangement permits the use of the device as a current limiting appliance, wherein it automatically opens a circuit vin response to an overloaded condition. The opening of the circuit likewise stops the heating of the strip which returns to normal position' and closes the contacts. If,

upon the'reestablishment of the circuit it is found that the overloaded condition persists, the strip .will rapidly flex again and reopen the circuit.

This cycle of operations will be repeated indelinitely until the overloaded condition is corrected. 'I'he intermittent operation above described will cause the flashing of lamps connected in the circuit and will in this manner call attention to tg condition of the circuit.

The functions of the electro-magnetic coil arrangement will now be explained. It will be seen that in the particular embodiment of the invention shown, the coil is connected in series with contacts 5 1. The coil may also be connected in parallel with the contacts or may be provided with a plurality of windings with both series and parallel connections. The current flow through the coil will establish a magnetic flux in core 9.

Brackets 8 and I3 and strip 4 which are separated from the core by the relatively thin insulators Il and I4 provide a magnetic path between the core and armature 6. With the coil Athe contacts as its temperature rises.

The Various ele- "ments are assembled as a rigid unit and are held A DECOD. may

accese? energized as it will be whenever there is any current flowing in the circuit with which the device is associated, armature 6 will be attracted to bracket 8 with a definite force. This force a opposes the tendency of strip d to flex and open In this Way it tends to maintain steady contact pressure. Strip 4 is so proportioned that when a predetermined current limit is exceeded, the torque exerted bythe strip will exceed the attractive force exerted on armature 4The contacts accordingly open andstop the current flow through the coil. The magnetic ux is dissipated and armaturey 6 is no longer attracted to bracket 8. The

thermo-flexible strip can now ex to its 1imitl5 tudinal magnetic ux through the contacts serves 20 to suppress the tendency to arc during the initial contact opening step and acts as a magnetic blow-cut in case an arc is found. Strip 4 cools,

y of course, with the circuit open, and, after a denite interval, recloses thecircuit. In case 25 circuit conditions are still adverse, the cycle of operations above described will be repeated.

Referring now to Fig. 2, the arrangement shown is generally similarto that of Fig. 1 except for the employment of two sets of contacts and the 30 centering of the electro-magnet core. The contacts are provided with separate adjusting means which permits individual regulation as to time and speed of .contact separation and also as to operating current limit. the same as the corresponding parts in Fig. 1. Screw 33 takes the place of`-core 9 and screws 3 and 20 of Fig. l. This screw is made of the same material as core 9 and serves both as core and one outside contact. Conductor 4 0 which corresponds to conductor I0 is wound on 'insulating sleeve 45'through which core 33 extends. The contact assemblies and their supporting brackets are exactly the same as those shown in Figs. 1 and 3. The electrical circuit of .this device may .be traced from-contact 33, bracket 38, contacts Aportion 6|,.metallic disc 53, to shell 32. While in' the present instance the two contacts have been shown connected in series, it willbe appreciated that eitherVV multiple or series-multiple conbe used instead when circuit conditions require. j

Having described my invention, what I consider new and desire to have protected by Letters Case 3l and shell 32 are 35 Patent will be pointed out in the appended-69 claim' s.

What is claimed is:

l. In combination, a fixed contact member, a movable contact member comprising a plurality of exible non-magnetic leaves and a magnetic leafengaging said fixed contact member, a thermoflexible element adapted to actuate said` movable contact member, and an electromagnet adapted to attract the magnetic leaf of said movable contact member.

2. In combination, a xed contact member, a movable contact member comprising a plurality of non-magnetic leaves and a magnetic leaf, each of said leaves engaging a different portion of said xed contactmember, a thermo-exible element 75.

connected in circuit with said contact members and adapted to exert a deiinite torque upon the movable contact member, and an electro-magnetic coil adapted to attract said magnetic leaf to counteract the torque exerted by said element.

3. A circuit controlling device comprising an electro-magnet, a pair of contact members, and a thermo-flexible element, wherein said contact members and said element are included in both the electrical and magnetic circuits of said magnet.

4. A circuit controlling device as claimed in claim 3 in which the thermo-:Eexible element and the electro-magnet apply opposing forces to the contacts.

5. A circuit controlling device as claimed in claim 3 in which arcing across the contacts upon their separation is inhibited by the magnetic eld passing through the contact members at the instant of opening.

6. A protective device comprising a xed contact member. a movable contact member actuated by a thermo-flexible element, a magnetic coil, a magneticcircuit for said coil including the core of said coil, the stationary and movable contact members and the contact supporting structure,

and means including said thermo-nexible element acting in opposition to said coil for separating said contacts by a suitable air gap when currents beyond a predetermined value are passed through the device.

'7. A circuit breaker comprising a xed contact. a movable contact actuated by a thermo-element, a magnetic coil, a core, an extension of said core comprising contact support portions, means for separating said contacts by a suitable air gap responsive to a pre-determined current iiow, and coacting means and including said coil support portions for compensating magnetically the contact pressure and movement supplied by the thermo-element.

8. 'I'he combination with movable multi-leaf contacts repeatedly and automatically opened and closed by current responsive elements, cooperating electro-magnetic and thermal means for equalizing contact pressure whereby said contacts are held closed below predetermined current values. and means for directing a magnetic flux between the leaves of the contacts upon the opening of the contacts to effect arc suppression.

9. A circuit controlling device comprising an electro-magnet, a thermo-flexible element with its supporting end clamped to the core of said magnet, a set of contacts controlledjointly by said magnet and said element, and an insulating case mounted on the core of said magnet enclosing the magnet, the element and the contacts.

10. A contact device comprising a multi-leaf contact element mounted on a stationary bracket of magnetic material, a multi-leaf contact element mounted on a thermo-flexible element and normally engaging said rst element, a second bracket supporting said thermo-ilexible element, a bridging member mounted on said thermoand said ilexibie element and extending to said iirst bracket to provide a magnetic path between the element and said first bracket, ai coil, a core extending through said coil, and means attaching said brackets to opposite ends of said core.

11. In a circuit controlling device. an electromagnet, a core for the netic material attached to one end of the cre, a thermal element attached to the other end of the core, a strip of magnetic material mounted on said element and cooperating with said bracket to complete the magnetic circuit of the magnet, and a pair of cis-operating contacts mounted respectively on said bracket and said element sol as to lie within the'inagnetic iield extending from said strip to said bracket. v

v12; A circuit controlling device comprising an electro-magnet, a fixed contact supported on the core of the magnet, a thermo-ilexible element attached to the core of said'magnet and carrying a contact adapted to engage `said xed contact, a bracket attached to the core of said magnet, and adiusting means attached to said bracket for exerting a variable tension on said element.

13. A circuit controlling device comprising an electro-magnet, a bracket of magnetic material attached to each end of the core of said magnet. each bracket having one end bent to lie substantially parallel with thev magnet core, a contact member attached to one bracket, a thermoexible element attached to one'end of the magnet core and carrying a contact member adapted to engage said first contact rmember, and a magnetic strip attached to said element to lie'sub stantially parallel to the magnet core and bridging the gap between the two bent ends of said brackets.

14. A circuit breaker comprising an electromagnet, a thermo-exible element and a contactl member attached to the core 'or said magnet, a contact member attached to said element and engaging said iirst contact member when "said element is in normal condition, rand an armature attached to said element and disposed within the ileld o! said magnet whereby the magnet is en-v abled to oppose'the separation of said contact members due to flexing of said element.

l5. A circuit controlling device comprising an electro-magnet, a thermo-ilexible element and a contact member attached to the core of said magnet, a contact member on said element engaging said nrst contact member, and an amature attached to said element and disposed so as to complete the magnetic circuit of said magnet.

16. A circuit controlling device having, in combination, an electro-magnet, a pair of contacts suported at one end of the magnet, a thermal element supported at the other end oi the magnet, and a pair of contacts carried by said thermal element and adapted to engage said ilrst contacts to complete respectively, an electrical circuit and a magnetic circuit for said magnet.

. EDWIN s. mon.

magnet, a bracket of mag 

